The motivation of LLP searches at the LHC in general and for constructing MATHUSLA in particular was extensively discussed in the physics case white paper [1]} and subsequent studies [2]}, [3]}, [4]}, [5]}, [6]}, [7]}, [8]}, [9]}, [10]}, [11]}, [12]}, [13]}, [14]}, [15]}, [16]}, [17]}, [18]}, [19]}, [20]}, [21]}, [22]}, [23]}, [24]}, [25]}, [26]}, [27]}, [28]}, [29]}, [30]}, [31]}, [32]}, [33]}. MATHUSLA can improve LHC reach by orders of magnitude in cross section and lifetime for LLP signal that are
trigger- or background-limited at the main detectors.For a recent discussion of LLP triggers at the LHC, see [34]}.
In this section we briefly review sensitivity estimates for some of the most important LLP benchmark models to demonstrate MATHUSLA's reach for probing new physics by discovering LLPs produced at the full range of energies access by the LHC, from the TeV- to sub-GeV-scale.The sensitivity estimates of the physics case white paper [1]} and many other studies assume the MATHUSLA geometry of the earliest proposals [36]}, [37]}, which differs from current benchmark geometry targeted by the MATHUSLA collaboration. However, the LOI Update [38]} demonstrated that the LLP sensitivity of the current geometry is essentially identical, and the earlier sensitivity estimates can be applied verbatim.
